a thing or person that helps increase or promote something, in particular 起推动(或推进)作用的事(或人),尤指 ■(Medicine)a dose of an immunizing agent increasing renewing the effect of an earlier one (医)增强辅剂量 ■the first stage of a rocket or spacecraft, used to give initial acceleration and then jettisoned (火箭,飞船的)助推器 ■a device for increasing electrical voltage or signal strength (电压,电讯号的)增压器,放大器 ■[incombination]a source of help or encouragement 推动,鼓励 job fairs are a great morale booster. 人才交流市场大大地鼓舞了人心。 ■(N. Amer.)a keen promoter of a person, organization, or cause (北美)积极的支持者;热心的拥护者